(19)
(11) EP 0 989 282 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
30.01.2002 Bulletin 2002/05

(43) Date of publication A2:
29.03.2000 Bulletin 2000/13

(21) Application number: 99307131.5

(22) Date of filing: 08.09.1999
(51) International Patent Classification (IPC)7: E21B 10/56
(84) Designated Contracting States:
AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE
Designated Extension States:
AL LT LV MK RO SI

(30) Priority: 24.09.1998 GB 9820693

(71) Applicant: Camco International (UK) Limited
Stonehouse, Gloucestershire GL10 3RQ (GB)

(72) Inventors:
  • Griffin, Nigel Dennis
    Whitminster, Gloucestershire (GB)
  • Matthias, Terry R.
    Upton St. Leonards, Gloucestershire (GB)

(74) Representative: Bailey, Richard Alan 
A.R. Davies & Co., 27 Imperial Square
Cheltenham, Gloucestershire GL50 1RQ
Cheltenham, Gloucestershire GL50 1RQ (GB)

   


(54) Improvements in preform cutting elements for rotary drag-type drill bits


(57) A preform cutting element for a rotary drill bit includes a facing table 37 of a superhard material having a rear surface 41 bonded to a substrate 38 of less hard material. A locking portion 39 projects from the rear surface 41 into the substrate 38, the substrate 38 and locking portion 39 having inter-engaging formations 40, 42 arranged to mechanically lock the facing table 37 to the substrate 38. The facing table may alternatively or additionally include a peripheral surface which is convexly curved, in cross-section, at least in the vicinity of a cutting edge thereof.






Search report